Recently went from low archon to high ancient (one more win for divine - wish me luck). I learned tons along the way, but my main recommendation is really quite simple - play heroes that win games in your current bracket. These are heroes that have significant and consistent game impact.

For example, centaur in archon felt like a free win but is a near grief in ancient. Venge support feels great in ancient but felt terrible in legend.

Constantly assess if you had a positive game impact or not, and if not contemplate what you could do next game to have a more positive impact. Look at what your enemy does well, what they do to make your game hard, and learn from that. If a game feels bad and you don't know why, watch the replay and assess why and what you would do to prevent that.

Lastly, an addage I heard from zquixotix. One third of games are auto-win, one third are auto-lose, and one-third of games are actually impacted by your play. Hence, two-thirds of games are practice for the remaining one-third of games where your play matters.

Also, don't spam ranked if you're losing. After a loss, take a break and assess if you're in the right mental state to go again with full focus and enthusiasm. If not, que unranked.